1. Field of the Invention
The present invention relates to a method and apparatus for a dental procedure, and, more particularly, to a method and apparatus for determining the dimensions of a root canal of a tooth.
2. Description of the Related Art
As is known, and referring to FIG. 1, pulp 14, the soft tissue that contains nerves, blood vessels and connective tissue, lies within a tooth 10 in the gum 20 and extends down from the crown 16 of the tooth thereof to the tip 18 of the root in the bone 12 of the jaw. When the pulp 14 is diseased or injured, and cannot repair itself, it dies. The most common cause of pulp death is a cracked tooth or a deep cavity 22, typically caused by decay. Both of these problems can result in germs/bacteria entering the pulp 14. Germs can cause an infection inside the tooth 10. Left without treatment, pus 24 builds up at the root tip 18 and can cause damage to the bone 12 around the infected tooth 10. When the infected pulp is not removed, pain and swelling can result. Certain byproducts of the infection can injure the jawbone. Without treatment, the infected tooth 10 may have to be removed.
One common method of treating the above-described infection before it reaches the bone 12 is to perform a dental procedure commonly referred to as a xe2x80x9croot canalxe2x80x9d treatment. This procedure involves removal of infected nerve and vascular tissue from a patient""s root canal 26 of the tooth 10 before such infected matter has a chance to further infect the patient""s bone 12 which is located adjacent to the root canal 26. This infected matter is removed from the root canal utilizing a drill fitted with an endodontic file. In particular, the endodontic file is manipulated to advance through the crown 16 of the infected tooth 10 until the endodontic file extends into the root canal 26. Thereafter, the endodontic file is manipulated within the root canal 26 until all of the infected nerve and vascular tissue are removed from the root canal 26. Once the nerve and vascular tissue are removed, the root canal 26 is sterilized and filled with an inert material and cement.
A problem with the above-described root canal procedure is that a clinician performing the procedure must ensure that the endodontic file reaches all of the infected areas of the root canal 26 without the endodontic file being erroneously advanced through a distal wall 30 (i.e. apical foramen) of the root canal 26. Therefore, in order to perform a root canal procedure correctly, it is important that the clinician know the length of the root canal 26 so that he/she does not over advance the endodontic file into the root canal 26 and thus drill a hole through the distal wall 30 (i.e. apical foramen) of the infected tooth 10 which may result in the infection being propagated to the bone 12.
Root canal therapy thus encompasses may clinical steps, each one predicated upon an accurate and precise determination of the length of the root canal of the tooth. From an accurate root canal measurement the clinician can determine the drilling distance and the point to which root canal fill material should be placed. This is termed the xe2x80x9cworking lengthxe2x80x9d. The working length is defined as the distance from a coronal (i.e. crown) reference point on the tooth to the point at which canal preparation and obturation should be terminated. Failure to determine an optimal root canal working length can lead to instrumentation short of the desired length with the result of tissue remnants being left in the root canal. Such failure to determine optimal root canal working length could also lead to long instrumentation with concomitant damage to the periradicular tissues, increased patient discomfort, potential for development of infection or inflammation, and the placement of irritating material beyond the confines of the tooth.
Heretofore, clinicians attempted to resolve the problem of determining root canal length by obtaining a conventional X-ray of the infected tooth and then estimating the length of the root canal by measuring the image of the root canal formed on the X-ray film. However, this approach suffers from the fact that most root canals are curved in such a way that an X-ray image is only two dimensional (i.e. the root canal is shown extending in the X and Y directions only), and it is common for the root canal to extend in a third dimension (i.e. the Z direction). Therefore, based on the data provided to the clinician by the X-ray image, it is still difficult for the clinician to determine the length of the root canal. This results in the likelihood that a clinician during a root canal procedure would either (i) over advance the endodontic file through the distal wall of the root canal of the infected tooth thereby creating a possibility that the bone will become infected, or (ii) under advance the endodontic file relative to the distal wall of the root canal thereby resulting in an amount of the infected nerve and vascular tissue not being removed from the root canal during the root canal procedure.
Thus, the generally accepted methods for determining the working length of a root canal are based on the placement of an endodontic file in the root canal and/or periapical radiographs. In using endodontic files, inaccurate placement of the stop and its angle can cause measurement error of 1 mm or more. Moreover, dental radiographs depict a two-dimensional (2-D) projection of the root canal, which can lead to errors in measurement for canals with significant curvature. An accurate measurement of length of the root canal requires a complete three-dimensional (3-D) description of the root canal.
What is needed is a technique and apparatus for an accurate 3-D measurement of the dimensions of a root canal.
The present invention provides a system and method for imaging and determining the dimensions of a root canal of a tooth. In particular, the present system and method generates a three dimensional mathematical model of a root canal by analyzing X-ray images. Thereafter, the dimensions of the root canal may be calculated based on the three dimensional mathematical model. This results in highly accurate imaging and measurement of the dimensions (i.e. length) of the root canal regardless of the anatomical shape of the root canal.
In one form thereof, the system includes a digital image (e.g. radiographic) sensor or transducer, a source of radiation such as an X-ray generator, and a computer or processing circuitry for receiving and storing digital X-ray images (radiographs) captured by the sensor and operating on the digitized images, and a display. The sensor is preferably an electronic type X-ray sensor.
In one form thereof, the method includes obtaining a first radiograph of the root canal by the digital image sensor upon exposure by generated X-rays which is digitized and stored by the computer. The first radiograph is representative of the root canal being interposed between the X-ray source and the image sensor at a first orientation. Thereafter, the source of radiation and image sensor is repositioned relative to the root canal so that the root canal is interposed between the source of radiation and the image sensor at a second orientation. Such repositioning may, for example, be between 5-40xc2x0 relative to the first position. The angular change in positioning can be either set by the operator or detected based on a three dimensional reference object embedded in the bite-olock. A second radiograph of the root canal is captured by the image sensor which is as well digitized and stored by the computer. The first and second digitized radiographs are processed by the computer to obtain a three dimensional mathematical model of the root canal. Thereafter, an image of the root canal may be shown on the display and/or the dimensions (e.g. length) of the root canal may be calculated by the computer. Such display and/or dimensions are then utilized by the clinician to carry out a root canal procedure.
In accordance with an aspect of the present method, after image acquisition, the computer processes the two radiographs and determines the edges of the root canal. The edges to each image are determined by one or all of: 1) either filtering for noise or searching and replacing dead and overexposed pixels with the mean gray level of neighboring pixels; 2) computing a single threshold of the entire radiograph for segmenting the radiograph; 3) using a morphological skeleton computation to obtain a central line of the root canal; and 4) modeling the root canal by an nth order polynomial. Once the edges for each image are detected and modeled, the 3-dimensional surfaces are computed by the use of a projection matrix for each image. The intersection of the 3-dimensional surfaces defines the 3-dimensional model of the root canal.
In accordance with an aspect of the present invention, once the 3-dimensional model of the root canal has been determined, it can either be displayed on the display or its dimensions (e.g. length and curvature) may be calculated.
An advantage of the present invention is the improved quality of root canal treatment by increasing the accuracy of working length measurement.
Another advantage of the present invention is the increased chance of detecting horizontal and vertical root fracture.
Yet another advantage of the present invention is the reduction of treatment time and cost.
Still further an advantage of the present invention is increased patient comfort and the reduction of radiation exposure.